Quick investigation: this is actually more related to demangleXXX family of
functions in std.traits
Their type system awareness seems a bit out of date :)

As far as I see, demangleParameterStorageClass has no problem.
In current, the set of valid parameter storage classes is (scope, out ref,
lazy).
And `inout` is always treated as a type qualifier, so is not contained the set.
On the other hand, demangleFunctionAttributes has the problem that just
reported here.
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In current, the set of valid parameter storage classes is (scope, out ref,
lazy).
And `inout` is always treated as a type qualifier, so is not contained the set.

Is there any single place on dlang.org or in TDPL where this can be read? I am
struggling to find proper classification of D type system since the very start
of work on fullyQualifiedTypeName.
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In current, the set of valid parameter storage classes is (scope, out ref,
lazy).
And `inout` is always treated as a type qualifier, so is not contained the set.

Is there any single place on dlang.org or in TDPL where this can be read? I am
struggling to find proper classification of D type system since the very start
of work on fullyQualifiedTypeName.

Mostly complete thing is here.
http://dlang.org/function#parameters
- const, immutable, share, and inout implicitly qualify the parameter type.
That means, foo(const T param) is implicitly translated to foo(const(T)
param).
After that, they will not remain as actual 'storage class'.
- The description >>'in' equivalent to 'const scope'<< is not correct.
With current compiler implementation, 'in' is just treated as 'const'.
So it's treated as a part of type, and will not remain as actual 'storage
class'
- Remaining four, 'ref', 'scope', 'lazy', and 'out' will have actual meanings
as 'storage class'.
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